• Journal of radiological science and technology
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• v.40 no.2
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• pp.311-316
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• 2017

Generally assessing bone mineral density (BMD) were performed on dual energy X-ray absorptiometry (DEXA) the same as dual energy CT (DECT) with a rapid-kVp switching. The purpose of this study is to compare the different of BMD value between DEXA and DECT method, and evaluate usefulness of DECT method. Using scanner for BMD measurements were GE, Healthcare Discovery 750 HD for DECT and Hologic QDR 4500W for DEXA. For compare BMD value in each method, scanned lumbar spine phantom and subjects visiting Korean National Cancer Center from April 2015 to December 2015, records of 50 patients. This study was approved by the Institutional Review Board. The mean BMD value measures for spine phantom and for subjects in each scanners presented strong correlation (r=0.948 with p<0.05 for phantom; r=0.635 with p<0.05 and Kendall's tau $({\tau})=0.46$ with p<0.05 for subjects) and linear relationship between DECT and conventional DEXA. DECT technique for BMD measurement will provide a very useful methodology without additional radiation dose.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.4
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• pp.181-192
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• 2003

We developed a mathematical simulation model to portray the vertical distribution of soil water from the measured weather data and the known soil hydraulic properties, and then compared simulation results with the periodically measured soil water profiles obtained on Jungdong sandy loam to verify the model, In this model, we solved potential-based Richards' equation by the implicit finite difference method superimposed on the predictor-corrector scheme. We presumed that: soil hydraulic properties are homogeneous; soil water flows isothermally; hysteresis is not considered; no vapor flows; no heat transfers into the soil profiles; and water added to soil surface is distributed along the soil profile following partial displacement principle. The input data were broadly classified into two groups: (1) daily weather data such as rainfall, maximum and minimum air temperatures, relative humidity and solar radiation and (2) soil hydraulic data to approximate unsaturated hydraulic conductivity and water retention. Each hydraulic polynomial function approximated using the Chebyshev polynomial and least square difference technique in tandem showed a fairly good fit of the given set of data. Vertical distribution of soil water as approximations to the Richards' equation subject to changing surface and phreatic boundaries was solved numerically during 53 days with a comparatively large time increment, and this pattern agreed well with field neutron scattering data, except for the surface 0.1 m slab.

• Journal of Chest Surgery
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• v.36 no.10
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• pp.748-753
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• 2003

Background: The pulmonary nodules (PN), when indicated, need thoracoscopic resection, especially in cases of non-diagnostic or technically infeasible PCNA (percutaneous needle aspiration). In the difficult situations of small or deeply seated PN, several techniques facilitating thoracoscopy have been used for detecting them. Our new protocol for managing PN was developed and prospectively reviewed. Material and Method: In the procedure of PCNA, we firstly placed the tip of the needle in the center of, or just in contact with PN under CT guidance, and loaded one or two segments of platinum radiomarker inside the needle after removing the stylet. Then, we forced the radiomarker to move to the tip of the needle by pushing the stylet. Finally, if the tip of the needle was not within PN, it was reoriented to the their center to obtain the sample for PCNA. Result: Between May 1999 and May 2000, radiomarkers were successfully placed in 28 PN of 26 patients, with the exception of one. In 18 (85%) of 21 nodules needing throacoscopy, intraoperative fluoroscopy was used to detect them or guide stapling resection during thoracoscopy. Conclusion: The advantages of this technique are that there is that there is no need for further localization for thoracoscopy even in cases of unsuccessful PCNA, and it was more effective in respect to both cost and time. Therefore, this strategy for PN expecting thoracoscopy will be helpful to patients and medical staff alike.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.484-491
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• 2013

In this paper, the method of designing a wideband antenna has been introduced through the design technique that simultaneously employs L- and slot-type feeds. Using the two kinds of feeds and additional fence structure, a compact wideband patch antenna has been realized. The size of the patch has been reduced by about 30 % based on the low frequency(824 MHz) and the full fractional bandwidth is wider than 100 %. The L-feed element is for the EM coupling feeding at the low frequency, while it functions as a feeding line for the power coupling through the slot at the high frequency. The proposed antenna has been designed not only for wideband operations but also for a proper array element with a reduced size. Thus, the foundation for developing the ultra wideband patch array antennas has been prepared. The fabricated antenna has been found to have good characteristics on V.S.W.R and the radiation patterns over the full bands. The experimental and computed results are shown to be in good agreement.

• Progress in Medical Physics
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• v.15 no.2
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• pp.100-104
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• 2004

The detector size effect due to the spatial response of detectors is a critical source of inaccuracy in clinical dosimetry that has been the subject of numerous studies. Conventionally, the detector response kernel contains all the information about the influence that the detector size has on the measured beam profile. Various analytical models for this kernel have been proposed and studied in theoretical and experimental works. Herein, a method to simply determine the detector response kernel using the Monte Carlo simulation and convolution theory has been proposed. Based on this numerical method, the detector response kernel for a Farmer type ion chamber embedded in a water phantom has been obtained. The obtained kernel shows characteristics of both the pre-existing parabolic model proposed by Sibata et al. and the Gaussian model used by Garcia-Vicente et al. From this kernel and deconvolution technique, the detector size effect can be removed from measurements for 6MV, 10${\times}$10 $\textrm{cm}^2$ and 0.5${\times}$10 $\textrm{cm}^2$photon beams. The deconvolved beam profiles are in good agreements with the measurements performed by the film and pin-point ion chamber, with the exception of in the tail legion.

• Progress in Medical Physics
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• v.23 no.3
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• pp.127-137
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• 2012

A conversing beam is firstly designed for radiosurgery by a neurosugern Lars Leksell in 1949 with orthogonal x-rays tube moving through horizontal moving arc to focusing the beam at target center. After 2 decades he composits 201 source of the Co-60 for gamma knife which beams focused at locus. Sveral linac-based stereotactic radiosurgery using the circular collimated beam which size range for 0.4~4.0 cm in a diameter by non-coplanar multiarc have been developed over the decades. The irregular lesions can be treated by superimposing with several spherical shots of radiation over the tumour volume. Linac based techniques include the use of between 4 and 11 non-co-planar arcs and a dynamic rotation technique and use photon beam energies in the range of 6~10 MV. Reviews of the characteristics of several treatment techniques can be found in the literature (Podgorsak 1989, Schell 1991). More in recent, static conformal beams defined by custom shaped collimators or a mini- or micro-multileaf collimator (mMLC) have been used in SRS. Finally, in the last few years, intensity-modulated mMLC SRS has also been introduced. Today, many commercial and in-house SRS programs have also introduced non-invasive immobilization systems include the cyberknife and tomotherapy and proton beam. This document will be compared the characteristics of dose distribution of radiosurgery as introduced gamma knife, BrainLab include photon knife in-house SRS program and cyberknife in currently wide used for a cranial SRS.

• Progress in Medical Physics
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• v.19 no.4
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• pp.241-246
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• 2008

Patient's respiration can have an effect on movement of tumor range and peripheral organs. Therefore, the respiratory signal was acquired by relation between external markers and movement of patient's abdomen during radiational therapy in order to minimize the effect of respiration. Based on this technique, many studies of rational therapy to irradiate at particular part of stable respiratory signals have executed and they have been clinically applied. Nevertheless, the phase-based method is preferred to the amplitude-based method for the rational therapy related to respiration. Because stabilization of the respiratory signal are limited. In this study, a in-house respiratory signal analysis program was developed for the phase reassignment and the analysis of the irregular respiratory signals. Various irregular respiratory patterns was obtained from clinical experimental volunteers. After then, the in-house program analyzed the factors affecting to phase assignment which is directly related to irradiated sector. Subsequently, accuracy of phase assignment was improved with removement of irregular signals by self-developed algorithm. This study is considered to be useful for not only image reconstruction and elevation of irradiating accuracy through phase assignment of RPM system but also analysis of respiratory signals. Moreover, development of 4D CT image is planed with phantom researches or clinical experiments based on this program.

• Journal of the Korean Society of Radiology
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• v.12 no.3
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• pp.343-349
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• 2018

Dose rate regulated tracking is known to be an efficient method which adaptively delivers tracking treatments when patient breathing is irregular. The Motion Management Interface (MMI, Varian Medical System, CA), which provides beam on/off switching during treatment is available for clinic. Study is to test if delivering the adaptive tumor tracking is feasible for irregular breathing using beam switching with MMI. 55 free breathing RPM traces acquired from lung cancer patients are used. The first day RPM traces of the patients are utilized to design preprogrammed tracking MLC patterns, of which periods are intentionally reduced by 20% in order to catch up the variation of patient breathing irregularity in the treatment day. Eligibility criteria for this technique are the variation of amplitude and period less than 20%. An algorithm which determines beam on/off every 100 ms by considering the preprogrammed (MLC) positions and current breathing positions is developed. Tracking error and delivery efficacy are calculated by simulating the beam-switching adaptive tracking from the RPM traces. Breathing patterns of 38 patients (70%) met the eligibility criteria. Tracking errors of all of the cases who meet the criteria are less than 2 mm (average 1.4 mm) and the average delivery efficacy was 71%. Those of rest of the cases are 1.9 mm and 48%. Adaptive tracking with beam switching is feasible if patient selection is based on the eligibility criteria.

• Journal of Yeungnam Medical Science
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• v.9 no.2
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• pp.312-320
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• 1992

Radiotherapeutically, nasopharyngeal cancer is an important disease in korea. Because of its blind anatomic location, early detection is relatively uncommon. Clinically, most of cases are locally advanced and nodal involvement are common. Recently better understanding of nature of the disease and improvement of radio-therapy technique permit better treatment results, including locoregional control and survival rate, and minimal normal tissue damages comparing with previously published data. We analyzed 31 patients of pathologically proven and previously untreated naso-pharyngeal carcinoma with different treatment techniques, retrospectively. Minimal and maximal follow up period of the survuor is 6 months and 68 months, respectively. Thirteen patients with squamous cell carcinoma are included in this analysis. The median age is 49 years(range from 20 to 64 years). Twenty two patients are stage III. Eleven patients are treated with radiotherapy alone and 20 are treated with comblined modalities treatment. The degree of responses after radiotherapy are categorized by 3-classes, i.e. complete response, partial response. In spite of simioarities of complete response rate and 1-year survival rate between two different treatment techniques, those patients with undifferentiated carcinoma appear to benefit from the adjuvant chemotherapy. In addition, systemic failure is more prominant in radiotherapy alone group than in combined modalities treatment group. These results suggest that adjuvant therapy in the radiotherapeutic management of nasopharyngeal cancers needs additional research according to histologic types and future extensive clinical trials.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.3
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• pp.331-337
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• 2018

The decommissioning of nuclear power plants is generally executed in five steps, including preparation, decontamination, cutting/demolition, waste disposal and environmental restoration. So, for efficient decommissioning of nuclear power plants, worker safety, effects compared to cost, minimization of waste, possibility of reuse, etc., shall be considered. Worker safety and measurement technology shall be secured to exert optimal efficiency of nuclear power plant decommissioning work, for which accurate measurement technology for systems and devices is necessary. Typical In-Situ methods for decommissioning of nuclear plants are CZT, Gamma Camera and ISOCS. This study used ISOCS, which can be applied during the decommissioning of a nuclear power plant site without collecting representative samples, to take measurements of the S/G Water Chamber. To validate the measurement values, Microshield and the GEANT4 code was used as the actual method were used for modeling, respectively. The comparison showed a difference of $1.0{\times}10^1Bq$, which indicates that it will be possible to reduce errors due to the influence of radiation in the natural environment and the precision of modeling. Based on the research results of this paper, accuracy and reliability of measurement values will be analyzed and the applicability of the direct measurement method during the decommissioning of NPPs will be assessed.